AMNH :: Browsing by Author "MacPhee, R. D. E."

Browsing by Author "MacPhee, R. D. E."

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Basicranial morphology and relationships of Antillean Heptaxodontidae (Rodentia, Ctenohystrica, Caviomorpha). (Bulletin of the American Museum of Natural History, no. 363)
(American Museum of Natural History., 2011-12-30) MacPhee, R. D. E.
What, if much of anything, are "Antillean heptaxodontids"? Over the course of nearly a century and a half, these caviomorph rodents, with their distinctive quasilamellar cheek teeth and generally large body size, have been diversely regarded as members of Chinchilloidea, or Cavioidea, or Octodontoidea; as distinct enough to warrant their own family or subfamily, or as no more than an offshoot within Dinomyidae or Capromyidae; and as having diverged from other caviomorph clades as early as the Oligocene, or as recently as the late Neogene. Similar uncertainties concern the taxonomic content of the group. It has been repeatedly suggested that the Antillean Heptaxodontidae as usually organized may be paraphyletic, but no adequate character-based arguments have appeared that might form a strong basis for reassessment. This paper attempts to arrive at some serviceable solutions to the heptaxodontid problem by utilizing the character-rich domain of the auditory region. Thus Amblyrhiza inundata (St. Martin/Anguilla) and Elasmodontomys obliquus (Puerto Rico), the chief subjects of this contribution, have traditionally been regarded as closely related on the basis of dental features. Yet certain basicranial characters, analyzed here for the first time, reveal that Amblyrhiza possesses derived features of bullar development and middle-ear vascularization that are found in this specific combination only in Chinchilloidea. These features are also seen in the Mio-Pliocene Patagonian taxon Eumegamys, reinforcing the position that it belongs in this grouping as well. The basicranial morphology of Elasmodontomys is rather primitive, and where it should be placed cladistically remains indeterminate, although its likeliest position is within Octodontoidea. Although it is taken for granted that no single set of morphological features will satisfactorily capture relationships throughout a large group like Caviomorpha, the absence of basicranial characters in most morphology-based systematic discussions of these rodents is glaring. The results reported here, while suggestive in their own right, should now be tested against much larger datasets.
Basicranial morphology of early Tertiary erinaceomorphs and the origin of primates. American Museum novitates ; ; no. 2921.
(New York, N.Y. : American Museum of Natural History, 1988) MacPhee, R. D. E.; Novacek, Michael J.; Storch, G.
Body size in Amblyrhiza inundata (Rodentia, Caviomorpha), an extinct megafaunal rodent from the Anguilla Bank, West Indies : estimates and implications. American Museum novitates ; no. 3079
(New York, N.Y. : American Museum of Natural History, 1993) Biknevicius, A. R.; McFarlane, D. A. (Donald A.); MacPhee, R. D. E.
Caudal cranium of Thylacosmilus atrox (Mammalia, Metatheria, Sparassodonta), a South American predaceous sabertooth. (Bulletin of the American Museum of Natural History, no. 433)
(American Museum of Natural History., 2019-06-14) Forasiepi, Analía M.; MacPhee, R. D. E.; Hernández del Pino, Santiago.
The caudal cranium of the South American sabertooth Thylacosmilus atrox (Thylacosmilidae, Sparassodonta, Metatheria) is described in detail, with emphasis on the constitution of the walls of the middle ear, cranial vasculature, and major nerve pathways. With the aid of micro-CT scanning of the holotype and paratype, we have established that five cranial elements (squamosal, alisphenoid, exoccipital, petrosal, and ectotympanic) and their various outgrowths participate in the tympanic floor and roof of this species. Thylacosmilus possessed a U-shaped ectotympanic that was evidently situated on the medial margin of the external acoustic meatus. The bulla itself is exclusively composed of the tympanic process of the exoccipital and rostral and caudal tympanic processes of the squamosal. Contrary to previous reports, neither the alisphenoid nor the petrosal participate in the actual tympanic floor, although they do contribute to the roof. In these regards Thylacosmilus is distinctly different from other borhyaenoids, in which the tympanic floor was largely membranous (e.g., Borhyaena) and lacked an enlarged ectotympanic (e.g., Paraborhyaena). In some respects Thylacosmilus is more similar to hathliacynids than to borhyaenoids, in that the former also possessed large caudal outgrowths of the squamosal and exoccipital that were clearly tympanic processes rather than simply attachment sites for muscles. However, hathliacynids also exhibited a large alisphenoid tympanic process, a floor component that is absent in Thylacosmilus. Habitual head posture was inferred on the basis of inner ear features. Large paratympanic spaces invade all of the elements participating in bounding the middle ear, another distinctive difference of Thylacosmilus compared to other sparassodonts. Arterial and venous vascular organization is relatively conservative in this species, although some vascular trackways could not have been securely identified without the availability of CT scanning. The anatomical correlates of the internal carotid in relation to other basicranial structures, the absence of a functional arteria diploetica magna, and the network for venous return from the endocranium agree with conditions in other sparassodonts.
Contributions to mammalogy in honor of Karl F. Koopman. Bulletin of the AMNH ; no. 206
([New York] : American Museum of Natural History, 1991) Griffiths, Thomas Alan.; Klingener, David.; Handley, Charles O.; Owen, Robert D.; Peterson, R. L.; Baker, Robert J.; Honeycutt, Rodney L.; Van Den Bussche, Ronald A.; Freeman, Patricia Waring.; Lemen, Cliff A.; Smith, Andrea L.; Novacek, Michael J.; Pacheco Torres, Victor R. (Victor Raul); Patterson, Bruce D.; Ryan, James M.; Anderson, Sydney.; Heaney, Lawrence R.; Hill, John E.; Morgan, Gary S.; Wilson, Don E.; Timm, Robert M.; Lewis, Susan E.; Lawrence, Marie A.; MacPhee, R. D. E.; Fleagle, John G.; Musser, Guy G.; Holden, Mary Ellen.; Voss, Robert S.; Myers, Philip.
Cranial morphology and phylogenetic relationships of Trigonostylops wortmani, an Eocene South American native ungulate (Bulletin of the American Museum of Natural History, no. 449)
(American Museum of Natural History., 2021-04-19) MacPhee, R. D. E.; Hernández Del Pino, Santiago; Bond, Mariano; Kramarz, Alejandro; Forasiepi, Analía M.; Sulser, R. Benjamin
In 1933 George G. Simpson described a remarkably complete skull of Trigonostylops, an Eocene South American native ungulate (SANU) whose relationships were, in his mind, quite uncertain. Although some authorities, such as Florentino Ameghino and William B. Scott, thought that a case could be made for regarding Trigonostylops as an astrapothere, Simpson took a different position, emphasizing what would now be regarded as autapomorphies. He pointed out a number of features of the skull of Trigonostylops that he thought were not represented in other major clades of SANUs, and regarded these as evidence of its phyletic uniqueness. Arguing that the lineage that Trigonostylops represented must have departed at an early point from lineages that gave rise to other SANU orders, Simpson reserved the possibility that Astrapotheriidae might still qualify (in modern terms) as its sister group. Even so, he argued that the next logical step was to place Trigonostylops and its few known allies in a separate order, Trigonostylopoidea, coordinate with Astrapotheria, Notoungulata, Litopterna, and Pyrotheria. Simpson's classification was not favored by most later authors, and in recent decades trigonostylopids have been almost universally assigned to Astrapotheria. However, his evaluation of the allegedly unique characters of Trigonostylops and its allies has never been systematically treated, which is the objective of this paper. Using computed tomography, the skull of Trigonostylops is compared, structure by structure, to a variety of representative SANUs as well as extant perissodactylans (which together comprise the clade Panperissodactyla) and the "condylarthran" Meniscotherium. In addition to placing Simpson's character evaluations in a comparative context, we also provide detailed assessments of many vascular and pneumatization-related feature of panperissodactylans never previously explored. Overall, we found that this new assessment strengthened the placement of Trigonostylops within a monophyletic group that includes Astrapotherium and Astraponotus, to the exclusion of other SANU clades. Although Trigonostylops cannot be considered as morphologically distinct or unusual as Simpson thought, our comparative and phylogenetic analyses have helped to generate a number of hypotheses about character evolution and function in SANUs that may now be fruitfully tested using other taxon combinations.
Domo de Zaza, an early Miocene vertebrate locality in south-central Cuba : with notes on the tectonic evolution of Puerto Rico and the Mona Passage. American Museum novitates ; no.3394
(New York, NY : American Museum of Natural History, 2003) MacPhee, R. D. E.; Iturralde-Vinent, Manuel.; Gaffney, Eugene S.
This report summarizes the results of paleontological and geological investigations carried out during the 1990s at Domo de Zaza, a late early Miocene vertebrate locality in south-central Cuba. Paleontologically, the most important result of fieldwork at Zaza was the first discovery of terrestrial mammals of Tertiary age in Cuba. Three terrestrial mammal taxa are now known from this locality--a megalonychid sloth (Imagocnus zazae), an isolobodontine capromyid rodent (Zazamys veronicae), and a platyrrhine primate (Paralouatta marianae, new species). In addition to these finds, a number of selachian, chelonian, crocodylian, cetacean, and sirenian remains have been recovered. Domo de Zaza is a low hill transected by a large artificial channel, the Canal de Zaza, whose walls provide an extensive exposure of Miocene sediments attributable to the Lagunitas Formation (Fm). This formation is laterally and vertically complex, showing evidence of at least four different depositional regimes. However, the sedimentary sequence indicates that all depositional phases took place within a broader episode of transgression. Estimated Burdigalian age (16.1-21.5 Ma) for Lagunitas Fm is based on the presence of marine invertebrate taxa corresponding to the late early Miocene Miogypsina-Soritiidae zone. The overall transgressive aspect of Lagunitas suggests rising sea level, possibly in correlation with a global onlap event. Within Burdigalian time, the most likely correlate is the eustatic rise centered on 17.5-18.5 Ma. Most of the vertebrate fossils were recovered from lagoonal and alluvial beds; those from lagoonal beds are exceptionally well preserved. The terrestrial facies displays evidence of paleosol formation, subaerial erosion, and plant life in the form of grass and palm pollen. Other evidence indicates that most of the present-day highlands of Cuba, including the Cordillera del Escambray near Zaza, have been continuously subaerial since the latter part of the late Eocene. Although no land vertebrate fossils of this age are known from Cuba, recent discoveries elsewhere in the Greater Antilles indicate that land vertebrates could have colonized landmasses in the Caribbean Basin as early as 33-36 Ma. Recently, marine geological data have been interpreted as showing that (1) the Mona Passage began to form in the early Oligocene, and (2) the Puerto Rico/Virgin Island block was entirely transgressed by shallow marine environments during the period between the late Oligocene and the early Pliocene. However, the seismic reflection profile evidence for an early Oligocene opening of the passage is ambiguous. Even if the separation of Puerto Rico and eastern Hispaniola occurred relatively early, it remains more probable than not that this happened in the medial Oligocene or even somewhat later (i.e., ≤30 Ma). On the other hand, the evidence is not at all ambiguous concerning the hypothesized mid-Cenozoic inundation of Puerto Rico: it did not happen. When available land and marine indicators are adequately compared, apparent contradictions in datasets can be evaluated and resolved. When examined in this way, the preponderance of evidence supports the contention that Puerto Rico has been an emergent landmass and has supported terrestrial environments continuously since the latest Eocene.
Exceptional skull of Huayqueriana (Mammalia, Litopterna, Macraucheniidae) from the late Miocene of Argentina : anatomy, systematics, and paleobiological implications. (Bulletin of the American Museum of Natural History, no. 404)
(American Museum of Natural History., 2016-06-22) Forasiepi, Analía M.; MacPhee, R. D. E.; Hernández del Pino, Santiago.; Schmidt, Gabriela I.; Amson, Eli.; Grohé, Camille.
The Huayquerías Formation (late Miocene, Huayquerian SALMA) is broadly exposed in west-central Argentina (Mendoza). The target of several major paleontological expeditions in the first half of the 20th century, the Mendozan Huayquerías ("badlands") have recently yielded a significant number of new fossil finds. In this contribution we describe a complete skull (IANIGLA-PV 29) and place it systematically as Huayqueriana cf. H. cristata (Rovereto, 1914) (Litopterna, Macraucheniidae). The specimen shares some nonexclusive features with H. cristata (similar size, rostral border of the orbit almost level with distal border of M3, convergence of maxillary bones at the level of the P3/P4 embrasure, flat snout, very protruding orbits, round outline of premaxillary area in palatal view, and small diastemata between I3/C and C/P1). Other differences (e.g., lack of sagittal crest) may or may not represent intraspecific variation. In addition to other features described here, endocast reconstruction utilizing computer tomography (CT) revealed the presence of a derived position of the orbitotemporal canal running below the rhinal fissure along the lateroventral aspect of the piriform lobe. CT scanning also established that the maxillary nerve (CN V₂) leaves the skull through the sphenoorbital fissure, as in all other litopterns, a point previously contested for macraucheniids. The angle between the lateral semicircular canal and the plane of the base of the skull is about 26°, indicating that in life the head was oriented much as in modern horses. Depending on the variables used, estimates of the body mass of IANIGLA-PV 29 produced somewhat conflicting results. Our preferred body mass estimate is 250 kg, based on the centroid size of 36 3D cranial landmarks and accompanying low prediction error. The advanced degree of tooth wear in IANIGLA-PV 29 implies that the individual died well into old age. However, a count of cementum lines on the sectioned left M2 is consistent with an age at death of 10 or 11 years, younger than expected given its body mass. This suggests that the animal had a very abrasive diet. Phylogenetic analysis failed to resolve the position of IANIGLA-PV 29 satisfactorily, a result possibly influenced by intraspecific variation. There is no decisive evidence for the proposition that Huayqueriana, or any other litoptern, were foregut fermenters.
The first Tertiary fossils of mammals, turtles, and fish from Canada's Yukon. (American Museum novitates, no. 3943)
(American Museum of Natural History., 2019-10-31) Eberle, Jaelyn.; Hutchison, J. Howard (John Howard), 1939-; Kennedy, Kristen.; Koenigswald, Wighart von.; MacPhee, R. D. E.; Zazula, Grant D.
Despite over a century of prospecting and field research, fossil vertebrates are exceedingly rare in Paleogene and Neogene rocks in northern Canada's Yukon Territory. Here, we describe the first records of probable Neogene vertebrate fossils from the territory, including tooth fragments of a rhinocerotid, a partial calcaneum of an artiodactyl, shell fragments of the pond turtle Chrysemys s.l. and tortoise Hesperotestudo, and a fragment of a palatine of Esox (pike). Although the tooth fragments cannot be identified solely by traditional paleontological means, we use tooth enamel microstructure, and primarily the presence of vertical Hunter-Schreger bands, to refer them to the Rhinocerotidae. As the only known record of the Rhinocerotidae in North America's western Arctic, the tooth fragments from the Wolf Creek site support the hypothesis that the clade dispersed between Asia and North America across Beringia. The fossils are consistent with a Miocene age for the Wolf Creek site that is inferred from radiometric dates of the Miles Canyon basalt flows in the vicinity of the fossil locality. Further, the tortoise and pond turtle fossils indicate a mild climate in the Yukon at the time, consistent with the vegetation reconstructions of others that indicate a warmer, wetter world in the Miocene than today.
First Tertiary land mammal from Greater Antilles : an early Miocene sloth (Xenarthra, Megalonychidae) from Cuba. American Museum novitates ; no. 3094
(New York, N.Y. : American Museum of Natural History, 1994) MacPhee, R. D. E.; Iturralde-Vinent, Manuel.
High resolution images for 'Exceptional skull of Huayqueriana (Mammalia, Litopterna, Macraucheniidae) from the late Miocene of Argentina : anatomy, systematics, and paleobiological implications. (Bulletin of the American Museum of Natural History, no. 404)'
(American Museum of Natural History., 2016-06-22) Forasiepi, Analía M.; MacPhee, R. D. E.; Hernández del Pino, Santiago.; Schmidt, Gabriela I.; Amson, Eli.; Grohé, Camille.
High resolution images for 'Exceptional skull of Huayqueriana (Mammalia, Litopterna, Macraucheniidae) from the late Miocene of Argentina : anatomy, systematics, and paleobiological implications. (Bulletin of the American Museum of Natural History, no. 404)' - http://hdl.handle.net/2246/6659
"Last occurrence" of the Antillean insectivoran Nesophontes : new radiometric dates and their interpretation. American Museum novitates ; no. 3261
(New York, NY : American Museum of Natural History, 1999) MacPhee, R. D. E.; Flemming, Clare.; Lunde, Darrin P.
"Several times during this century it has been claimed on the basis of anecdotal evidence that some of the allegedly extinct endemic mammals of the Greater Antilles still survive in remote areas. To investigate this possibility, an attempt was made in 1996 to locate living representatives of the island-shrew genus Nesophontes (Insectivora, Nesophontidae) in the Sierra de Baoruco, Dominican Republic. The attempt was unsuccessful. However, in a related project, it was found that nesophontid remains from Cuba and Hispaniola, judged to be very recent on associational grounds, were in fact much older (12th-15th centuries AD) according to AMS 14C dating. This information, combined with other evidence discussed here, suggests that species of Nesophontes may have collapsed extremely rapidly, close to the time of the first European entry into the West Indies. We discovered no direct evidence that predation by or competition with Old World rats or other exotic species caused nesophontid extinctions. Neither recent collecting efforts nor radiometric evidence support the view that any island-shrew species survived into the 20th century"--P. [1].
Late Cenozoic land mammals from Grenada, Lesser Antilles island-arc. American Museum novitates ; no.3302
(New York, NY : American Museum of Natural History, 2000) MacPhee, R. D. E.; Singer, Ronald.; Diamond, Michael (Michael K.), 1957-
We report on a small collection of late Cenozoic fossil vertebrates recovered from a lahar (mudflow) deposit at Locality 12° North on the southern coast of Grenada. ⁴⁰K/⁴⁰Ar-dated hornblende concentrate from the lahar deposit yielded age estimates of 2.6-3.7 Ma (late Pliocene). Although these estimates date crystallization of the hornblende and not the lahar event, the latter is unlikely to be substantially younger. The contained fauna is here regarded as latest Pliocene or slightly younger. Dental specimens in the collection are readily referable to Hydrochaeridae (Rodentia, Caviida) and Megalonychidae (Xenarthra, Phyllophaga), groups heretofore unknown on this island. The capybara, Hydrochaeris gaylordi, new species, differs from extant Hydrochaeris hydrochaeris in the conformation of the maxillary second molar. The sloth teeth (two caniniforms, one molariform) notably differ from one another in size, but whether they represent one species or two cannot be decided on this evidence. Because of the limitations of the material, attribution of the specimens to subfamily or tribe within Megalonychidae is also uncertain. Megalonychid sloths have never been found previously on any of the Lesser Antilles, although they formed part of the terrestrial vertebrate fauna of most of the Greater Antilles. Curaçao is the only other island in the Caribbean Sea that has yielded sloth and capybara fossils. Sloths and capybaras might have reached that island as well as Grenada by short-distance over-water transport, perhaps during a time of lowered sea level. A late land connection with South America is perhaps possible, but this would need to be confirmed with suitable geological evidence.
Late Quaternary fossil mammals from the Cayman Islands, West Indies. (Bulletin of the American Museum of Natural History, no. 428)
(American Museum of Natural History., 2019-03-04) Morgan, Gary S.; MacPhee, R. D. E.; Woods, Roseina.; Turvey, Sam.
Abundant fossils of nesophontid lipotyphlan insectivores and capromyid rodents have been collected from late Quaternary deposits on the Cayman Islands, an island group separated by a major marine barrier from other Caribbean landmasses and isolated from anthropogenic impacts until the arrival of Columbus in 1503 CE. These collections have not previously been formally described. Using morphological and ancient DNA approaches, we document three new taxa of extinct endemic terrestrial mammals from this island group: Nesophontes hemicingulus (Grand Cayman and Cayman Brac), Capromys pilorides lewisi (Grand Cayman, Little Cayman, and Cayman Brac), and Geocapromys caymanensis (Grand Cayman and Cayman Brac). Morphometric comparisons with other extinct and living West Indian mammals indicate that the biogeographic origins of all three new taxa are from source populations on Cuba. Ancient DNA data indicate very low sequence divergence of Capromys pilorides lewisi from mainland Cuban C. pilorides (only 0.5% across the entire mitogenome). Using probabilistic analysis of existing and new radiometric dates, we calculate an estimated extinction date of 1700 CE (95% confidence interval = 1632-1774 CE) for the Cayman Brac Capromys population. This result suggests that at least one endemic Cayman terrestrial mammal population survived for well over a century following first European arrival in the Cayman Islands. The West Indies lost nearly all its species-rich late Quaternary land mammal fauna during the late Holocene due to direct or indirect human impacts, and this study provides a new baseline to understand the magnitude of human-caused mammal extinctions during the recent past.
Morphology, adaptations, and relationships of Plesiorycteropus : and a diagnosis of a new order of eutherian mammals. Bulletin of the AMNH ; no. 220
([New York] : American Museum of Natural History, 1994) MacPhee, R. D. E.
"Plesiorycteropus, an extinct mammal known only from the Quaternary of Madagascar, is conventionally regarded as a tubulidentate and therefore as closely related to extant Orycteropus. However, the shared derived traits that might support such an association have never been adequately identified or critically evaluated. The character analyses presented in this paper reveal that many of the identifiably derived traits of the skeleton of Plesiorycteropus are related to adaptations for digging. Aardvarks possess many of the same adaptations, but so do fossorial members of a broad diversity of other eutherian groups, including Dasypodidae, Manidae, Myrmecophagidae, Lipotyphla, and many others. Identifiably derived traits of Plesiorycteropus that have no obvious connection with digging are few, but the ones that can be adequately documented are by no means unique to aardvarks. Indeed, several of the apparently derived cranial and postcranial traits of Plesiorycteropus specifically echo conditions encountered in primitive ungulates, including various members of the paraphyletic assemblage Condylarthra. Accordingly, the view that Plesiorycteropus is unambiguously aardvarklike in its morphology and adaptations is not supported in this study. To examine how a parsimony analysis of a stated character set might specify a placement for Plesiorycteropus, a 30-character, 16-taxon data matrix was formatted for the program Phylogenetic Analysis Using Parsimony. Two additional characters, based on morphological assessments of key characters made by Bryan Patterson, were also used in some runs. Although the scale of morphological variation in Plesiorycteropus requires the recognition of two species, P. madagascariensis and P. germainepetterae n. sp., for the characters under consideration interspecific polymorphism was usually found to be negligible. Although in most manipulations of the data matrix Plesiorycteropus tended to group with ungulates sensu lato (including Tubulidentata), its placement was unstable, and an exclusive sister-group pairing of Plesiorycteropus + Tubulidentata was rarely encountered. On the other hand, close pairings with xenarthrans, manids, and lipotyphlans did not occur unless the data matrix was purposely biased in those directions. As a minimum hypothesis, it may be concluded that Plesiorycteropus is apparently part of the great ungulate 'bush,' but a more exact placement is not convincingly provided by any of the cladistic solutions investigated. One resolution of this problem would be to refer Plesiorycteropus to superorder Ungulata as incertae sedis, but this would make it the only Recent mammal lacking a recognized ordinal affiliation. An alternative would be to consider Plesiorycteropus to be the sole known member of its own order. This is the resolution preferred here, on the ground that Plesiorycteropus is as morphologically distinctive as any eutherian group currently granted ordinal status. The new order Bibymalagasia is created for its reception"--P. 6.
Mortality in a predator-free insular environment : the dwarf deer of Crete. (American Museum novitates, no. 3807)
(American Museum of Natural History., 2014-06-30) Geer, Alexandra van der, 1963-; Lyras, G. A. (George A.); MacPhee, R. D. E.; Lomolino, Mark V., 1953-; Drinia, Hara.
Age-graded fossils of Pleistocene endemic Cretan deer (Candiacervus spp.) reveal unexpectedly high juvenile mortality similar to that reported for extant mainland ruminants, despite the fact that these deer lived in a predator-free environment and became extinct before any plausible date for human arrival. Age profiles show that deer surviving past the fawn stage were relatively long-lived for ruminants, indicating that high juvenile mortality was not an expression of their living a "fast" life. Although the effects on survivorship of such variables as fatal accidents, starvation, and disease are difficult to gauge in extinct taxa, the presence of extreme morphological variability within nominal species/ecomorphs of Candiacervus is consistent with the view that high juvenile mortality can function as a key innovation permitting rapid adaptation in insular contexts.
A new astrapothere (Mammalia, Meridiungulata) from La Meseta Formation, Seymour (Marambio) Island, and a reassessment of previous records of Antarctic astrapotheres. (American Museum novitates, no. 3718)
(American Museum of Natural History., 2011) Bond, Mariano.; Kramarz, Alejandro.; MacPhee, R. D. E.; Reguero, Marcelo.
During the past quarter century, the uplifted nearshore sediments comprising the Eocene La Meseta Formation (LMF) of Seymour (Marambio) Island have produced a diverse assemblage of terrestrial mammals that closely, but not exactly, resembles late Early Eocene faunas from southern Patagonia. This assemblage includes the only astrapothere and litoptern fossils known from outside South America. The occurrence of astrapotheres in LMF was originally indicated by fragmentary dental remains tentatively referred to family Trigonostylopidae on the basis of their general resemblance to the Patagonian genus Trigonostylops Ameghino. In this contribution we describe a new astrapothere specimen from LMF; unlike specimens collected previously, this one is a complete and excellently preserved lower cheek tooth, providing a basis for a review of all previous records of Astrapotheria from this formation. This tooth (probably p4 rather than m1) is sufficiently distinct from all other known astrapothere cheek teeth to warrant assignment to a new genus and species, Antarctodon sobrali. It has a transversally elongated entoconid, resembling that observed in at least one specimen of the Mustersan genus Astraponotus, but the tooth as a whole is much lower crowned and less lophodont than in the latter. Phylogenetic analysis suggests that Antarctodon is closer to genera classified by previous authors as astrapotheriids (e.g., Albertogaudrya and Tetragonostylops) than it is to Trigonostylops. Reexamination of other LMF specimens previously referred to Trigonostylopidae reveals that some specimens are attributable to this new taxon and others either are not astrapotheres at all or lack distinctive features. Consequently, at present the record of order Astrapotheria in Antarctica should be considered as restricted to non-trigonostylopids.
New craniodental remains of the Quaternary Jamaican monkey Xenothrix mcgregori (Xenotrichini, Callicebinae, Pitheciidae), with a reconsideration of the Aotus hypothesis. American Museum novitates ; no.3434
(New York, NY : American Museum of Natural History, 2004) MacPhee, R. D. E.; Horovitz, Inés.
The Jamaican monkey Xenothrix mcgregori is one of several extinct endemic platyrrhines known from the late Quaternary of the Greater Antilles. Until recently, the hypodigm of Xenothrix was limited to the holotype partial mandible and a handful of tentatively referred postcranial elements. Here we describe several additional fossils attributable to Xenothrix, including the first cranial remains, all of which were recovered in cave deposits in the Jackson's Bay region of southern Jamaica. In addition to a partial face from Lloyd's Cave and a maxillary fragment of a different individual from the same site, the craniodental collection includes two incomplete mandibles with poorly preserved cheekteeth from nearby Skeleton Cave. The new specimens confirm a distinctive derived feature of Xenothrix, i.e., reduced dental formula in both jaws (2/2 1/1 3/3 2/2). Although no examples of the maxillary canine are yet known, its alveolus is notably small. Similarly, although the upper face of Xenothrix is also unknown, it is clear that the maxillary sinuses were large enough to encroach significantly on the bases of the zygomatic processes. The nasal fossa is also very large and wider than the palate at the latter's widest point. A similar condition is seen in the extinct Cuban monkey Paralouatta varonai. Xenothrix continues to generate disputes among platyrrhine specialists because its unusual combination of apomorphies complicates its systematic placement. Rosenberger's recent "Aotus hypothesis" stipulates that Xenothrix is a close relative of the living owl monkey (Aotus) and is not a pitheciid sensu stricto. Two fundamental characters used to support this hypothesis--hypertrophied orbits and enlarged central incisors--can be shown to be inapplicable or uninterpretable on the basis of the existing hypodigm of Xenothrix. The new craniodental evidence confirms our earlier cladistic results showing that the Antillean monkeys (Xenothrix mcgregori, Paralouatta varonai, and Antillothrix bernensis) are closely related and that Callicebus is their closest joint extant mainland relative. This may be expressed systematically by placing the three Antillean taxa in Xenotrichini, new tribe, adjacent to Callicebini, their sister-group within subfamily Callicebinae (Pitheciidae).
A new genus for the extinct Hispaniolan monkey Saimiri bernensis Rímoli, 1977 : with notes on its systematic position. American Museum novitates ; no. 3134
(New York, N.Y. : American Museum of Natural History, 1995) MacPhee, R. D. E.; Horovitz,Ines.; Arredondo, Oscar.; Vasquez, Osvaldo Jimenez.
New megalonychid sloths (Phyllophaga, Xenarthra) from the Quaternary of Hispaniola. American Museum novitates ; no.3303
(New York, NY : American Museum of Natural History, 2000) MacPhee, R. D. E.; White, Jennifer L. (Jennifer Lynn); Woods, Charles A. (Charles Arthur)
As part of ongoing revisionary work on Antillean Megalonychidae, we document four new sloth species from Quaternary cave localities in Haiti and the Dominican Republic. The new taxa and their tribal affiliations are as follows: Megalocnus zile (Megalocnini), Acratocnus ye (Acratocnini), and Neocnus dousman and N. toupiti (Cubanocnini). Significantly, each is closely related to species in genera long known from Cuba. This observation is of primary biogeographical importance because the most parsimonious explanation for the presence of parallel arrays of lower-level clades of sloths on opposite sides of the Windward Passage is vicariance, not a series of uncoordinated over-water dispersals. For a brief period in the late Paleogene, eastern Cuba, northern Hispaniola, Puerto Rico, and the Aves Rise formed a large positive structure (GAARlandia) that was evidently briefly continuous with northwestern South America. We infer that the later subdivision and subsidence of major portions of GAARlandia must have finely vicariated its biota (which included sloths at least as early as the early Oligocene). On this argument, Megalocnus, Acratocnus, Neocnus, and Parocnus (= Mesocnus) must have already been in existence as independent clades at the time of origin of the Windward Passage (early Neogene), because cladistically diagnosable members of these taxa occur in Quaternary contexts in both Cuba and Hispaniola. This interpretation is consistent with several new lines of evidence concerning the paleontological and paleogeographical history of the Caribbean region.

Browsing by Author "MacPhee, R. D. E."

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